This invention generally relates to a method of controlling an evaporative heat exchanger. More particularly, this invention relates to a control scheme for operating an evaporative heat exchanger that exhausts to space vacuum.
Evaporative heat exchangers are utilized in applications where a conventional radiator cannot be utilized. An evaporative heat exchanger includes a cooling medium that accepts heat from another system and exhausts that heat to an ambient environment. Water is a very efficient cooling medium with a latent heat of 1000 BTU/lb (2326.000 J/kg). The favorable latent heat to weight ratio makes water a suitable choice for use in vehicles operating in extreme conditions with restrictive space and weight requirements.
The conditions in which evaporative heat exchangers are utilized in a space vacuum are at the extreme thermodynamic conditions for water. Slight changes in pressure and temperature can result in freezing of water within the evaporator. For this reason great care must be taken to maintain operation of the evaporative heat exchanger within desired performance ranges.
Accordingly, it is desirable to design and develop a method and device for adapting evaporative heat exchanger operation to current operating conditions to maintain desired performance.